document major improvements of release 0.26.0

[dthv]

There are a few points of the 0.26.0 release that are not fully documented, yet, including:

• dashboard (needing full coverage)
• erase tool
• text shapes
• disable scroll to zoom (maybe within a "touch support" section?)
• co-DM option
• mark shape as defeated
• tracker bars
• import dungeondraft *.dd2vtt / *.svg
• mac keybindings
• public_name config option
• big red border when disconnected
• unique floor names

[dthv]

Campaign Settings → Admin will probably need a new screenshot that includes granting a player DM access.

[dthv]

It would be prudent to wait for #78 and #79 to be merged prior to working on the three remaining issues (mark shape as defeated, tracker bars, import dungeondraft format and svg) as these will need touching files modified in these PRs.